TDD pattern configuration

[Miguel Cantero López]

Hello,

I am trying to configure the TDD pattern and I have some questions.

To configure it, the instruction is the next one, extracted from some cttc examples:

nrHelper->GetGnbPhy (enbNetDev.Get (0), 0)->SetAttribute ("Pattern", StringValue (tddPattern));

The pattern is stored in the variable tddPattern. One example of this variable could be: 

"DL|DL|DL|S|UL|DL|DL|DL|S|UL|"

My questions are:

   1. What does this values represent? The subframes or the symbols? 5G has huge flexibility and you can configure both subframes and symbols, but I am not sure what I am configurating with this instruction.

In case the example above configures the subframes...

   2. What is the difference between F and S? Does it mean F is composed by 14 F symbols and S is a mix of UL, DL and F symbols?

   3. Where do you specify the symbols combination in a special subframe?

Thanks in advance,

Miguel

[Katerina Koutlia]

Hi Miguel, 

TDD is set per slot. 

The difference between F and S is:

In an F slot the first and the last OFDM symbols are reserved for DL CTRL and UL CTRL, respectively (e.g., DCI and UCI). The symbols in between can be dynamically allocated to DL and UL data, hence supporting dynamic TDD. 

S slots are implemented basically to emulate LTE. In those slots, the first symbol is reserved for DL CTRL, the last symbol is reserved for UL CTRL, and the rest of the symbols are available for only DL data. 

Note that, the DL CTRL can be one or more symbols and UL CTRL can also be 1 or more symbols - depends on how many DL/UL CTRL symbols you configure. Default value is 1 for DL CTRL and 1 for UL CTRL. For DATA you may have 1 or more symbols.

The combination is specified in the scheduler (check nr-mac-scheduler-ns3). 

You can also have a look in the NR Documentation. To generate it please follow the instructions included in README.md

BR,
Kat

--
You received this message because you are subscribed to the Google Groups "5G-LENA-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email to 5g-lena-user...@googlegroups.com.
To view this discussion on the web, visit https://groups.google.com/d/msgid/5g-lena-users/93ca8b1d-356c-47a8-8e60-429ea68f0f07n%40googlegroups.com.

[Sandra Lagén]

Hi Miguel,

Responses in line.

BR,

Sandra

Missatge de Miguel Cantero López <miguel....@fivecomm.eu> del dia dv., 11 de juny 2021 a les 13:54:

Hello,

I am trying to configure the TDD pattern and I have some questions.

To configure it, the instruction is the next one, extracted from some cttc examples:

nrHelper->GetGnbPhy (enbNetDev.Get (0), 0)->SetAttribute ("Pattern", StringValue (tddPattern));

The pattern is stored in the variable tddPattern. One example of this variable could be: 

"DL|DL|DL|S|UL|DL|DL|DL|S|UL|"

My questions are:

   1. What does this values represent? The subframes or the symbols? 5G has huge flexibility and you can configure both subframes and symbols, but I am not sure what I am configurating with this instruction.

SL: They represent the slots. For example "DL|DL|DL|F|UL|" means there are 3 Downlink slots, followed by a flexible slot, and last one Uplink slot.

In case the example above configures the subframes...

   2. What is the difference between F and S? Does it mean F is composed by 14 F symbols and S is a mix of UL, DL and F symbols?

SL: F is a totally flexible slot, in which, out of the 14 OFDM symbols, we may have DL control, DL data, UL data and UL control. The order is first DL and then UL, but the number of DL data and UL data symbols is actually flexible, depending on the scheduling decision. S is the special slot of LTE, just in case one wants to configure LTE TDD. S slot is composed of DL control, DL data and UL control, so it has no space for UL data.

   3. Where do you specify the symbols combination in a special subframe?

SL: In F slot, the number of symbols for DL data and UL data is flexible, upon the scheduling decision. If you want, you could pre-configure maximum values for the number of DL and UL symbols within an F slot, and send us the patch for potential integration. But, in the current code, it is like all the symbols for data, are F symbols, and once the scheduling decision is done, first will come the DL data symbols, and close to the last UL control would come the UL data symbols.

[Miguel Cantero López]

Hello Kat and Sandra,

Thanks for the responses. I found it very useful.

I still do not have very clear how to configure the pattern beyond the slots. By this I mean, for example, how to proceed if I want to simulate a DUDU pattern half-slot defined (7 OS). How can I split a slot into half downlink and half uplink?

Thank you,

Regards,

Miguel

[Sandra Lagén]

Hi Miguel,

This case cannot be configured with the current code. But what you can try is: configure an FFFFF pattern (all slots as flexible) and then in the scheduler (nr-mac-scheduler-ns3.cc) define two new attributes: maximum number of DL symbols per F slot, and maximum number of UL symbols per F slot. And then, limit the number of OFDM symbols within the scheduler, allocated to DL and UL by such two attributes. Check that the scheduling phase is not affected by that, and that all works properly. It is just an idea, on how to handle this. Basically, with such changes, all slots will have a pattern of 7 OS DL and 7 OS UL.

BR,

Sandra

Missatge de Miguel Cantero López <miguel....@fivecomm.eu> del dia dl., 14 de juny 2021 a les 12:47:

To view this discussion on the web, visit https://groups.google.com/d/msgid/5g-lena-users/21c7501c-d186-43d5-8eba-2b93065c8737n%40googlegroups.com.

[Tae-Hoon Kwon]

Hello :) Sandra Lagén

I'm wondering about possibility of allocating UL/DL in one F symbol in LENA.
For instance, UL is put inside the DL symbol to improve UL performance.
What i would like to say, Is it possible to simultaneously allocate UL/DL within one symbol?

We appreciate if you explain which codes or functions shall be modified in order to configure the DL part and guard RB and the UL part and guard RB and the DL part in one symbol?


Best regards,
Kwon

2021년 6월 14일 월요일 오후 9시 54분 15초 UTC+9에 Sandra Lagén님이 작성: